Oldest example I can remeber comes from "Flame of recca" Tokiya Mikagami can use a "magogu" (weapon) that uses water to form it's blade, on emergencies he can create a blood sword with his own blood which makes him more powerful.

I was referring to the whole series.
The concept sucks, the artist is a genius, she gives the flow to the series.
Only thing that has kept me waiting for chapters, because they don't even publish the volumes together.
Following this **** since 2008 haven't been easy...